The invention relates to a high-temperature-resistant synchronous belt. The high-temperature-resistant synchronous belt comprises a synchronous belt frame and a rubber material covering the synchronous belt frame. The raw material of the rubber material comprises, by weight, 10-20 parts of polyester glycol, 50-100 parts of diisocyanate, 10-20 parts of dicarboxylic anhydride, 10-20 parts of diamine, 1-5 parts of catalysts, 0.1-1 part of graphene, 0.2-5 parts of silicon carbide and 0.05-0.1 part of cross-linking agent. The invention further relates to a preparation method of the high-temperature-resistant synchronous belt. According to the high-temperature-resistant synchronous belt and the preparation method, due to the fact that an imide functional group is introduced to a main chain of a polyurethane material, the rigidity of a polyurethane hard segment can be effectively enhanced, the ordered structure of the hard segment cannot be easily destroyed, and the mechanical performance and the high temperature resistance performance of the rubber material of the synchronous belt are greatly improved; due to the fact that the cross-linking agent, namely octo-isocyanate modified silsesquioxane is used, the stress borne by the rubber material can be borne within a large range, the stress burden in a rubber material body is reduced, and the shear strength and the abrasion resistance of the synchronous belt are effectively improved.